# -*- coding =utf-8 -*-
# @Time : 2022/9/12 17:42
# @Author :1814-09胡海燕
# @File : 2-1.py
# @Software : PyCharm
sc = int(input("请输入学生成绩(百分制)："))
if 100 >= sc >= 90:
    print('A')
elif sc >= 80:
    print('B')
elif sc >= 70:
    print('C')
elif sc >= 60:
    print('D')
else:
    print('E')
